Bistable semiconductor multivibrator circuit



BIsTABLE sEMIcoNDUcToR MULTIVIBRATOR CIRCUIT Filed oct. 22, 1949 lNov. 2l, 1950 R. P. MOORE, JR

2 Sheets-Sheet l A a f F 6 IVI I l l l l l I l .lll ml u L nl WH wf wn w ,MII 1%/ :IM/IMI. Mlll IllW 4, -lll 1 lill @Hl lL L i M y w m .M M w a m w 1|||||| 11| |||M m||||||l| l|x| w W M m7. nw ,4% Wwf@ 6 m z l- 1 i I w l 1 4 w IO 0 1 0 f 01 0 z 0 N j M M f ,W w M :inventor amozaE/Vorg Cttorneg Nov. 2l, 1950 R. P. MooRE, JR

BISTABLE SEMICONDUCTOR MULTIVIBRATOR CIRCUIT Filed oct. 22, 1949 2 Sheets-Sheet 2 ENQ Nn wwf MN YJ u w e, m W m mM a 1m .Mm m Wj R \N\ l IIRIIWII" Q w. NEN' b1 m atented Nov. 2l, 1950 asa-Lott BISTABLE SEMICONDUCTOR MULTI- YIBRAI'OR CIRCUIT Raymond P. Moore, Jr., West Collingswood, N. I., assignor to Radio Corporation of America, a

corporation of Delaware Application october 2z, 1949, serial No. 123,076

This invention relates generally to relaxation oscillators, and more particularly relates to a bistable multivibrator .of the type including two semi-conductor devices.

In a copending application of E. Eberhard, Serial No. 121,552, iled on October 15, 1949, and assigned to the assignee of this application, various multivibrator circuits have been disclosed which make use 'of semi-conductor devices. Among the multivibrator circuits disclosed in the Eberhard application is a bistable multivibrator, that is, a multivibrator which has two stable states of operation. Thus, a bistable multivibrator may be triggered alternately from one stable state of operation to the other by the application of triggering impulses. A multivibrator circuit of this type is also known as a iiip-fiop circuit or as a multivibator of the Eccles-Jordan type. A bistable multivibrator circuit finds application, for example, in counter circuits where it is desired to count impulses occurring either at regular intervals or at random. A circuit of this type must be stable. Furthermore, the ease with which the trigger pulses may be applied is an important consideration for such counter circuits. In the Eberhard multivibrator, the trigger pulses must be applied simultaneously to corresponding electrodes of the two-semiconductor devices of the circuit. For a cascade-connected counter it is usually desirable to apply the trigger pulses to a single electrode only.

It is accordingly a principal object of the present invention to provide an improved bistable multivibrator circuit including two semi-conductor devices.

Another object of the invention is .to provide a bistable multivibrator circuit of the type referred to which will be more stable than previous multivibrator circuits of the semi-conductor types.

A further object of the invention is to provide a bistable multivibrator circuit which may be triggered by input pulses of either' polarity or by pulses of mixed polarity impressed on one electrode only of one of the two semi-conductor devices of the circuit, thereby to render the circuit more adapted foruse in a multi-stage impulse counter.

A bistable multivibrator circuit in accordance with the invention comprises two semi-conductor devices each having a base electrode, an emitter electrode and a collector electrode in contact with a semi-conducting body. Individual resistors are provided in circuit with each of the electrodes of the two devices and energizing potentials are applied to the electrodes, as is conventional. Furthermore, the base electrode of each device is cross connected to the collector electrode of the'other device by an 7 claims. (ci. ivisti 4In accordance with theY present invention, the` two emitter electrodes are interconnected or coupled by an impedance element, such as a capacitor. This capacitor renders the circuit more stable and aids in the rapid transfer of the condition of high conductivity from one device to the other device upon lthe arrival of a trigger pulse. The trigger pulses may either be of positive or of negative polarity or of ymixed polarity and preferably are applied to the base electrode of the first device while the output pulses are preferably .derived from the collector electrode of the second device. No change in bias is required to make multivibrator circuit responsive to pulses of either polarity.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof will best be understood from the following description when read in connection with the drawing, in which:

Figure 1 is a circuit diagram of a bistable multivibrator circuit embodying the present invention;

Figure 2 is a graph illustrating the voltages at the electrodes of two semi-conductor devices of the circuit of Figure l;

Figure 3 is a block diagram of a multi-stage impulse counter for developing one output pulse in response to a certain number of input pulses, and which may function as a decade counter, being one illustration of a counter embodying the circuit of the invention;

Figure 4 is a detailed circuit diagram of the impulse counter of Figure 3; and

Figure 5vis a graph illustrating the pulses developed at the various stages of the counter of Figure 4.

Referring now to the drawings, in which like components have been designated by the same reference numerals throughout the figures, and paricularly to Figure l, there is illustrated a bistable multivibrator circuit in accordance with the invention comprising a first semi-conductor device I!) and a second semi-conductor device Il. The first semi-conductor device I0 includes body I2 of semi-conducting material which may consist, for-example, of boron, silicon, germanium, tellurium or selenium containing a small but sufiicient number of atomic impurity centers or lattice imperfections as commonly employed for best results in crystal rectiers. Germanium is the preferred material for body I2 and may be prepared so as to be an electronic N type semi-conductor. as is well known.

The surface of semi-conducting body I2I may be polished and etched in a conventional manner. It is also feasible to utilize the germanium block o! a comercial high-'back-voltage germanium rectifier such as the typelN34. in which case further surface treatment may not be required. It is also feasible to treat body I2 in the manner disclosed and claimed in the copending application to Barton, Serial No. 118,428, illed on September 28, 1949, and assigned to the assignee of this application. Body I3 of the second semiconductor device I I may consist of the same material as does body I2 and may be treated in the same manner.

Semi-conducting body I2 of semi-conductor device I is provided with emitter electrode I4, collector electrode I5 and base electrode I5. Emitter electrode I4 and collector electrode I5 are usually small-area electrodes and may be point contacts consisting, for example, of tungsten or Phosphor bronze wires having a diameter of the order of 2 to 5 mils with a pointed tip. However, it is not essential that emitter electrode I4 and collector electrode I5 are small-area electrodes provided they make rectifying, high-resistance contacts with body I2. Emitter and collector electrodes I4 and I5 are ordinarily placed closely adjacent to each other on the same surface of body I2 or on opposite surfaces thereof, in which case they may be separated -by a distance of from 2 to 5 mils.

Base electrode I6 provides a low-resistance, non-rectifying contact with the bulk material of semi-conducting body I2 and usually is a largearea electrode. Similarly, the second semi-conductor device II is provided with emitter electrode I8, collector electrode I9 and base electrode 20 which may be constructed andarranged in the same manner as the corresponding electrodes of device III.

A comparatively large, reverse bias voltage is impressed between associated collector and base electrodes. Thus, assuming that bodies I2 and I3 consist of N type germanium which is presumed to havea P type surface layer, the collector electrodes must be biased negatively with respect to their associated base electrodes. To this end, there is provided battery 22 having its positive terminal grounded and by-passed for alternatingfrequency currents by capacitor 23. The negative terminal of battery 22 is connected to collector electrode I5 through resistor 24 and also to collector electrode I9 through resistor 25. Resistors 26 and 21 individually connect base electrodes I6 and 20, respectively, to ground.

A comparatively small forward bias is provided between the emitter electrodes and their associated base electrodes. Assuming again that bodies I2 and I3 consist of N' type germanium which is assumed to have a P type surface layer. the emitter electrodes must normally have a positive potential with respect to their associated base electrodes. To this end separate bias batteries may be provided for devices I0 and II Since base electrode I6 normally has a negative potential with respect to ground due to the voltage drop across resistor 26 battery 30 has its positive terminal grounded while its negative terminal is connected to emitter electrode I4 through l resistor 3 I Battery 30 may be shunted by by-pass vcapacitor 32. Another battery 33 is provided for biasing emitter electrode I8 in a similar manner and has its positive terminal grounded while its negative terminal is connected to emitter electrode I8 through resistor 34. Capacitor 35 by- ,passes battery 33 for alternating-frequency currents.

Resistor 31 is connected between collector electrode I5 of device I0 and base electrode 20 of device II. Similarly, resistor 38 is connected between collector electrode I9 of device II and base electrode I6 of device I0. In accordance with the present invention capacitor 4I) interconnects the two emitter electrodes I4 and I8.

Trigger pulses developed by pulse generator 4I and illustrated at 42 may be applied across base resistor 26 by coupling capacitor 43. The trigger pulses illustrated at 42 are of positive polarity, but it is to be understood that the circuit may also be triggered by the application of negative trigger pulses. The out put pulses or square topped waves are derived from collector electrode I9. Preferably the output pulses are differentiated by differentiating network 45 including capacitor 46 connected to collector electrode I9 and shunt resistor 41 having one terminal grounded.

The output pulses derived from differentiating network 45 may be applied to a second counter stage similar to the one shown in Figure l. In this case, it is desirable to remove the pulses of undesired polarity obtained from differentiating network 45. The desired pulses may, for example, be of positive polarity. Thus, the pulses of positive and negative polarity derived from network 45 may be applied to a crystal rectifier 48 which functions as a clipper and removes the negative pulses. The direct current return path of the clipper circuit is completed by shunt resistors 41 and 50 each having one terminal grounded.

Thel pulses are derived across resistor 5I) and may be impressed on another counter stage through series resistor 5I and blocking capacitor 53 and may be obtained from output terminals 53. The positive output pulses are shown at 54. It is to be understood that differentiating network 45 includes the shunt resistance represented by resistor 50 and by any shunt resistance which may exist in output terminals 53.

The operation of the multivibrator circuit of Figure l will be better understood by reference to Figure 2. In Figure 2 Eer-1. Erm, Em. Em, Een and Em indicate respectively the voltages of emitter electrode I4. base electrode I6 and co1- lector electrode l5 of the first device I I) and of emitter electrode I8, base electrode 20 and collector electrode I9 of the second device II with respect to time.

Let it now be assumed that de'vice I0 conducts current heavily while device II conducts current lightly. Upon the arrival of a positive trigger pulse 42, the voltage of base electrode I6 goes in a positive direction as shown by curve portion 56 (Figure 2). This in turn will cut oil the current conduction through device I0 because the voltage between emitter electrode I4 and base electrode I6 becomes too small to permit the flow of current. Since current no longer flows through collector resistor 24, the voltage of collector electrode I5 goes in a negative direction as shown by curve portion 51 (Figure 2). Accordingly, the voltage of base electrode 20 also goes in a. negative direction because collector electrode I5 and base electrode 2li are coupled through resistor 31. This aisance is uiustrated by curve portion sa of Figure 2. `As' 'electrode is which may soon as the voltage oi base electrode 20 becomes more negative, device II will conduct more current and accordingly the voltage of collector elec,-

trode I8 becomes'more positive due to the voltage drop across collector resistor 2i as illustrated by curve portion 80. This positive going collector voltage is now impressed through coupling resistor 38 on base electrode I6, which in turn becomes still more positive. Thus, the feedback path is regenerative and the current conduction through device Ill is consequently cut oil very quickly while the current through device Il increases rapidly.

be differentiated by di!- `ierentiating network 46 and passed through a clipper or crystal rectier 48 so that positive output pulses 64 may be obtained from output terminals 63. It will, o! course, be understood that 'one output pulse is obtained for every pair of trigger pulses. The multivibrator circuit of Figure 1 may be triggered by the application oi trigger pulses to base electrode I6, and itis not Upon the arrival of the trailing edge of the input pulse 42, base electrode I8 becomes slightly more negative as indicated at 6I in 4Figure 2. This in turn will permit device I8 to conduct a small amount of current. A new stable state of operation has now been reached will continue until the arrival of the next trigger pulse 42. Device I is now in a state of low conduction while device Il is in a state of heavy conduction.

Upon the arrival of the next trigger pulse 42, the potential of base electrode I6 again becomes more positive as illustrated at 62. However, the positive trigger pulse will have little effect on device I8 which is already in a state of low current conduction. This positive trigger pulse is now applied through coupling resistor 38 to collector electrode I9, the voltage of which will rise in a positive direction as indicated at 63 in Figure 2. This rise of voltage of collector electrode I9 cuts off device II because the potential between collector electrode I9 and its base electrode 28 is slightly reduced. i

The trigger action is further facilitated by the provision of coupling capacitor 40. The arrival of the positive trigger pulse 42 will also increase the potential of the emitter electrode I4 in a positive direction as shown by curve portion 64. This positive going pulse appearing on emitterv electrode I4 is now impressed through coupling capacitor 40 on emitter electrode I8 as shown by curve portion 65. The voltage of emitter electrode I8 is now more positive. Capacitor 48 and resistor 34 have such circuit constants as to function as a, difierentiator network for the pulse 64 appearing on emitter electrode I4.

The trailing edge of the positive pulse 64 on emitter electrode I4 is caused by the trailing. edgeof trigger pulse 42 and is differentiated and applied to emitter electrode I8. Consequently,

the voltage of emitter electrode I8 drops as shown by curve portion 66. This in turn tends to cut off device I I due to the reduced potential between emitter electrode I8 and base electrode 20. Thus, device I I is cut oi by the trailing edge of trigger pulse 42 and the voltage of collector electrode I9 becomes quite negative as shown by curve portion 61. This in turn causes a drop of the voltage of base electrode I6 as shown by curve portion 68.

It is to be understood that it is essential for the operation of the multivibrator circuit of the invention that at thisv point of the operating cycle, device I8 conducts a certain amount of current. Only under those circumstances will a positive going pulse appear on emitter electrode I4 which is then diierentiated and applied to emitter electrode I8.

The multivibrator circuit is now again in tis original state of stable operation in which it will continue until the arrival of the next trigger pulse whereupon the cycle of operation will repeat. As clearly shown in Figure 2, a substantially square wave 60, 61 is developed at collector necessary to apply the trigger pulses to correspending electrodes of devices I@ and Ii simultaneously.

Preferably, the resistance of base resistor 26 is larger than the resistance of base resistor 21. Furthermore, the resistance of coupling resistor 38 is preferably smaller than the resistance. of coupling resistor 31. Consequently. a large trigger pulse is developed across base resistor 28 which is impressed through coupling resistor 38 on collector electrode I9, thereby to facilitate the transfer of the trigger pulses to collector electrode I9. The multivibrator circuit of Figure 1 is accordingly unsymmetrical. It will also be understood that -coupling capacitor 48 may be omitted in which case the circuit will operate as described provided the resistance of resistor 28, 21 and 31, 38 have the relative values indicated above, However, the circuit without capacitor 48 will be less stable.

It has been found that it is also feasible to trigger the multivibrator circuit ol' Figure 1 by the application of negative trigger pulses to base electrode I6. Thus. when device I0 is conducting lightly while device II is conducting heavily, a

negative trigger pulse will drive device I8 into will have little effect on device I0, but the negative trigger pulse also appears on collector electrode I9 thus increasing the current ilow through device I I which in turn will cut oir device I0. Capacitor 40 acts again in a manner similar to that previously described. Thus, the negative trigger pulse will appear on emitter electrode I4. The trailing edge oi the trigger pulse is differentiated by capacitor 40 and resistor 34 and impressed on the emitter electrode I8 as a posil. tive pulse which further increases the current ilow through device II.

The multivibrator circuit of Figure 1 may, for example, be used in amulti-stage impulse counter of the type illustrated schematically in u Figure 3. The impulse counter of Figure 3 has a so 15 connected in cascade.

pair of input terminals 10 on which trigger pulses 1I of either positive polarity as illustrated or of negative polarity may be impressed. The impulse counter includes four stages 12, 13, 14 and Individual clipper 1stages 16, 11, 18 and 80 are connected to the output of each counter stage. stage may include a crystal rectifier such as shown in Figure l. Positive output pulses 8| o5 may be obtained from output terminals 82.

The first two counter stages 12 and 13 may be identical with the multivibrator circuit of Figure 1 as will be fully explained in connection with Figure 4. The second two counter stages 14 and 16 may, for example, consist of the flipiop circuitdisclosed and claimed in a copending application of E. Eberhard Serial No. 90,685, filed on April 30, 1949, and assigned to the assignee of this application. However, it is to be understoodthat stages 12, 13 and stages 14'.

Each clipper 7 'I3 may be exchanged or that all four stages may be identical.

Theimpulse counter as described will operate in a conventional manner and each stage will develop one output pulse in response to two input pulses. Consequently. the entire counter of Figure 3 will develop one output pulse for 24 or` 16 input pulses. However, it is also feasible to arrange the impulse counter of Figure 3 as a decade counter so that one output pulse is developed in response to every input pulses. To this end, there may be provided a first pulse generator 83 connected through clipper 84 to the output of the third counter stage 14. The output signal of pulse generator 83 may be impressed through switch 85 on the second counter stage 13. Furthermore, a second pulse generator 88 is connected through clipper 84 to the output of the fourth counter stage 15. The output signal developed by the second pulse generator 88 is connected through switch 88 to the third counter stage 14 and also through lead 90 to the rst pulse generator 83.

Pulse generators 83 and 88 preferably consist of a relaxation oscillator of the type disclosed and claimed in a copending application to E. Eberhard, Serial No. 70,661, led on January 4, 1949, and assigned to the assignee of this application.

When switches 85 and 88 are closed, the impulse counter of Figure 3 functions as a decade counter and its operation will now be explained by reference to Figure 5.

In Figure 5 to which reference is now made the input pulses 1| have been indicated at A. The pulses or square-topped waves shown at B, C, D and E indicate respectively the waves derived from the collector electrodes of the first stage 12, the second stage 13, the third stage 14 and the fourth stage 15. The pulses shown at F and G indicate the output waves derived from the iirst pulse generator 83 and from the second pulse generator 88. The Wave shown at H indicates the pulse which is impressed through lead 90 from the second pulse generator 88 on the first pulse generator 88.

An inspection of the wave shapes shown at B indicates that on the occurrence 0f every even trigger pulse 1I a positive going pulse is developed by the iirst stage 12 which is terminated upon the arrival of the succeeding odd trigger pulse. Accordingly, the second stage 13 receives an input pulse corresponding to the arrival of each leading edge of a pulse of wave B. However, a sharp pulse 95 occurs in wave C on the arrival of the fourth trigger pulse. This pulse is caused by the first pulse generator -83 which is triggered by the negative going or trailing edge 88 of wave D which is developed by the third stage 14. This trailing edge 96 triggers pulse generator 83 to develop a sharp positive pulse 36 (shown at F) which is impressed on the second stage 13. Accordingly. pulse 91 immediately triggers the second stage 13 back into its original position, and the second stage 13 is now ready to be triggered again on the occurrence of the 6th input pulse.

It will be observed that wave D also includes a sharp pulse |00 which occurs on the arrival of the 6th trigger pulse. This sharp pulse -I00 is due to the provision of the second pulse generator 86 which is coupled to the output of the fourth stage 15. Pulse generator 86 is responsive to the negative going or trailing edge |0I of wave E and develops a positive pulse |02 in response thereto.

This positive pulse |02 triggers the third stage 14 back into its original state thereby producing the sharp pulse |00. The third stage accordingly responds again to the arrival of the tenth output pulse.

It is essential that improper operation of the impulse counter of Figure 3 be prevented. Thus. the sharp pulse |00 represents a. positive going transition which is immediately followed by a. negative going transition. However. the negative going transititcn of the output pulse of stage 14 may tend to lire the first pulse generator 83 which is coupled thereto, thus producing a pulse on wave F in synchronism with the sixth trigger pulse. In order to prevent this, the differentiating circuit provided between the third stage 14 and the rst pulse generator 83, which develops negative pulses to trigger the pulse generator, has a suiiiciently long time constant so that it will not respond to the very narrow pulse |00. In addition a, negative blanking pulse |03 indicated in line H is derived from the second pulse generator 88 and applied to the rst pulse generator 83 so as to oppose any residual trigger pulse and to insure that pulse generator 83 is not triggered upon the arrival of the sixth trigger pulse.

Referring now to Figure 4, there is illustrated a detailed circuit diagram of the impulse counter of Figure 3. The first countrr stage 12 is substantially identical with the bis-table multivibrator of Figure 1. However, the two emitter electrodes I4 and I8 are provided with a common bins network |05, as is conventional. Network |05 consists of resistor |06 shunted by capacitor |01 and connected between ground on the one hand and emitter resistors 3| and 34, on the other hand. A common collector voltage supply 22 shunted by capacitor 23 is provided for all counter stages and pulse generators.

Since counter stage 12 operates in the same manner as the multivibrator of Figure 1 a further explanation of its operation is unnecessary here. The output signal is derived from collector electrode I9 and is passed through clipper 16 which is identical with the clipper circuit illustrated in Figure l. Capacitor 46 and resistor'41 again function as a differentiating network. Accordingly, the differentiated and clipped pulses derived from'stage 12 are impressed through resistor 5| and capacitor 52 connected in series on the base electrode I6a of the next counter stage 13. Stages 12 and 13 are identical so that further explanation of the second stage is not necessary here. Corresponding circuit elements and parts of stage 13 have been given the same reference numerals as were used in stage 12 except that each numeral has been provided with the aihx A. The output pulse derived from the second stage 12 is again differentiated and clipped by clipper 11 and impressed on the third stage 14.

The third stage 14 is a flip-flop circuit which may be considered a bistable multivibrator, that is, a circuit having two stable states of operation. However, the nip-flop circuit of stage 14 includes but a single semi-conductor device IIIl having an emitter electrode III, a collector electrode I I2 and a base electrode I I3. The base electrode I I3 is grounded through a resistor I I4. Collector electrode I|2 is connected to the negative terminal of battery 22 through resistor I|5. Emitter electrode III is grounded through resistor I|6 and bias network |I1 including variable resistor I I8 shunted by capacitor |20. Emitter electrode III and collector electrode IIZ are interconnected by capacitor MI and resistor electrode ||2 through resistor 5|a and capacitor 52a. connected in series.

The operation of the ilip-ilopcircuit 14 has been fully explained in the copending application to Eberhard. Serial No. 90,685 above referred to. The circuit 14 is arranged to have two stable states of operation, one corresponding to a low conduction state and one corresponding to a high conduction state. This is obtained by the provision o! base resistor ||4 and coupling resistor |22. Upon the arrival o! a trigger pulseimpressed on collector electrode I I2 the circuit is triggered from low to high conduction. The circuit is triggered again by the arrival of a succeeding trigger pulse, from high to low conduction; Consequently, the collector voltage becomes still more positive and due to the provision of capacitor |23 the circuit cannot lock again in its high conduction state and thus returns to its low conduction state.

The output pulses are obtained from collector electrode ||2 and are fed through differentiating capacitor |25 to clipper 18. Clipper 18 includes crystal rectifier |26, the input electrode of which is maintained at a predetermined negative potential by resistors |21 and |28 connected seriallyl between battery 22 and ground. The bias voltage of rectifier |28 prevents the positive pulses from variable tap |54 on resistor |52. Resistor |55 is connected between variable tap |52 and from stage 13 appearing on collector electrode 2 from being passed by the rectifier. Resistor |30 completes the direct current return path of the rectier. Clipper 18 accordingly passes only positive pulses which have been differentiated by capacitor |25 and resistor |28 and which have an amplitude exceeding the bias voltage of the rectiiler. It is to be understood that clippers 18 and 11 may be biased in the manner just described in connection with clipper 18. The thus obtained output pulses are fed through resistor |3| and capacitor |32 to collectorelectrode 2a of the last or fourth stage 15, which is identical with stage 14. Corresponding elements and parts of circuit 15 have been 'given the same reference numerals as have been used in stage 14 except that they have been provided with an amx a.

The output pulses derived from the fourth stage 15 are again passed through clipper 8|) which is identical with clipper 18, and the output pulses of the last stage may be derived from output terminals 82.

As indicated in Figure 3, the second pulse generator 88 is coupled through clipper 81 to the fourth counter stage 15. Thus lead is connected'to collector electrode ||2a of the fourth stage 15 and is coupled through coupling capacitor |38 to clipper 81. Clipper 81 includes crystal rectier |31 having both electrodes grounded through resistors |38 and |40. It will be observed that rectifier |31 is inverted with respect to the rectiiers of clippers 18 or 80 and accordingly a negative pulse isderived from clipper 81 which is impressed through resistor |4| and capacitor |42 on base electrode |43 of pulse generator 488.

Pulse generator 86 further includes emitter electrode |44 and collector electrode |45. Base electrode |43 is grounded through resistor |48.

Collector electrode |45 is connected to battery 22 through resistor |41. Furthermore, collector electrode |45 is grounded through capacitor |48.

The bias voltage for emitter electrode |44 is ob tained from voltage divider |50 including resistors |5|, |52 and |53 connected between battery 22 and ground. The emitter bias voltage is derived emitter electrode |44. Capacitor |58 is connected between variable tap |84 and ground for bypassing alternating-frequency currents.

Pulse generator 88 is a relaxation oscillator of the type disclosed and claimed in the Eberhard application, Serial No. 70,661 above referred to. Its operation has been explained in a paper by Webster, Eberhard, and Barton which appears in the March 1949 issue of RCA Review on pages 5 to 16 (see particularly pages 14 to 16).

The relaxation oscillator or pulse generator 88 is triggered by a negative pulse applied to its base electrode |43. Output pulses may be derived from collector electrode |45 through lead |80. which interconnects collector electrode |45 with collector electrode ||2 of the third counter stage 14 through capacitor IBI, resistor |82, switch 88, resistor |83 and capacitor |84. Accordingly, counter stage 14 is triggered by the pulses developed by the generator 86. Furthermore, another output pulse may be derived from emitter electrode |44 through lead 90. This pulse is utilized for the purpose explained hereinbefore and may be impressed through capacitor |68 and resistor |81 on emitter electrode |44a of the first pulse generator 83 which may be identical with the second pulse generator 86. Corresponding parts have been designated with the same reference numerals except that those for pulse generator 83 bear the afx a. Pulse generator 83 is triggered from the output pulses derived from the third stage 14. To this end lead |10 connects collector electrode ||2 through coupling capacitor |1| to clipper 84, which is identical with clipper 81. Accordingly, negative pulses are obtained from clipper 84 and impressed through capacitor |42a and resistor |4|a on base electrode |43a of pulse generator 83. The output pulses are obtained from collector electrode |45a of pulse generator 83 and are impressed through resistor |82a, capacitor |8|a, switch 85 and resistor |12 to base electrode 20a of counter stage 13.

Itis believed that the operation of the impulse counter of Figure 4 will now be obvious in view oi' the previous explanations.

While it will be understood that the circuit specifications of the impulse counter of Figure 4 may vary according to the design for any particular application, the following circuit specications are included by way of example only:

Voltage o1' battery 22 volts-- -45 First stage 72 Resistor 28 ohms 10.000 Resistor 3 do- 5,600 Resistor 24 do 10,000 Resistor |08 1 do 1,800 Resistorv 34 do 2,200 Resistor 25 do 10,000 Resistor 21 do 2,100 Resistor 31 -..do 56,000 Resistor 38 do 15,000 Capacitor 43 microfarads-- .1 Capacitor 40 do .001 yCapacitor |01 do 25 Capacitor 48 micromicrofarads-- 820 Clipper 76 Resistor 41 ohms 82,000 Resistor 50 do 39,000 Resistor 5| do 5,600 Capacitor 52 microfarads-- .0i

Second stage 73 Resistor 20a ....ohms-- 1,800 Resistor Sia do 2,700 Resistor |06a do 390 -Resistor 34a do 560 Resistor 24a do 22,000 Resistor -25a do 10,000 Resistor 01a do 39.000 Resistor 38a. -..do 2,2004 Resistor 21a ..-do 2,200 Capacitor 40a.. -microfarads-- .001 Capacitor |01a do .1 Capacitor 46a micromicrofarads 820 Clipper 77 Resistor 41a ohms-.. 82,000 Resistor 50a -do 39,000 Resistor 5in rin 1,000 Capacitor 52a .micromicro1arads 680 Third stage 74 .l

Resistor lll ohms 6,800 Resistor IIS dn 1,800 Resistor ||8 do 2,500 Resistor |22 do 22,000 Resistor ||5 do 15,000 Capacitor |20 microfarads-- 25 Capacitor |2| -micromicrofarads-- 330 Capacitor |23 ..-do 560 Capacitor |25 do 820 Clipper ?\8 Resistor |21 Lohms-- 1,800,000 Resistor |20 do 82,000 Resistor -do 39,000 Resistor |3| do 470 Capacitor |32 -micromicrofarads 680 Fourth stage 75 Resistor lila -ohms-- 8,200 Resistor ila -do 1,800 Resistor ||8a dn 2,500 Resistor |2241 do 22,000 Resistor ||a dn 27,000 Capacitor |a microfarads 25 Capacitor |2|a .micromicrofarads B30 Capacitor |2341 A do 560 Capacitor |a --do 820 Clipper 80 Resistor |21a ohms-- 1,500,000 Resistor |28a do 82,000 Resistor |30a do 1,000

Clipper 87 Capacitor |30 micromicrofarads-- 680 Resistor |38 ohms-- 82.000 Resistor |00 dn 89,000 Resistor iii do 560 Capacitor |42 microfarads-.. .01

Second pulse generator 86 Resistor |46 ohms-- 10,000 Resistor |41 -do 33,000 Resistor |5| -do 82,000 Resistor |52 do 5,000 Resistor |53 do 8,200 Resistor |55 do 820 Capacitor |56 mierofarads-- .1 Capacitor |48 do .001 Capacitor |8| do .1 Resistor |02 ohms-- 1,500 Resistor |63 do 1,500 Capacitor |60 -microfarads- .001 Capacitor |60 --do .01 Resistor |61 ohms., 10,000

Clipper 84 Capacitor |1| micromicrofarads 680 Resistor |40a -ohms-- 82,000 Resistor |38a do.. 39,000 Capacitor |4241 microfarads .01 Resistor Illa ohms-- 470 Firstpulse generator 83 Resistor |48a ohms-- 3,300 Resistor |41a do 10,000 Resistor -|55a do 470 Resistor |5|a ..-do 3,900,000 Capacitor |08a microfarads .01 Resistor |62a ohms-- 470 Capacitor |8|a microfarads-- .01 Resistor |12 ohms-- 470 'I'he total lcurrent consumption of the impulse counter of Figure 4 amounts to 18 milliamperes only corresponding to a power of approximately 800 milliwatts.

There has thus been disclosed a bistable multivibrator circuit which may be triggered by input pulses of either polarity or of mixed polarity impressed on one electrode only oi one of the two semiconductor devices of the circuit. The multivibrator circuit is more stable in operation than previously known semi-conductor multivibrator circuits. The multivibrator circuit of the invention may be used with advantage in an impulse counter, such as a decade counter.

What I claim is:

1. A bistable multivibrator circuit comprising a iirst and a second semi-conductor device, each having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in contact with each body, a source of potential, a rst pair of impedance elements, each being connected `between one terminal oi' said source and one of said collector electrodes, a second pair of impedance elements, each being connected between the other terminal of said source and one oi said base electrodes, said source being so poled as to apply a reverse bias potential between each collector electrode and its associated base electrode, means for applying a forward bias potential between each emitter electrode and its associated base electrode, a rst pair of resistors, each being connected between the base electrode ofv one of said devices and the collector electrode of the other device to provide regenerative feedback paths and a, further coupling impedance element interconnecting said emitter electrodes.

2. A bistable multivibrator circuit comprising a first and a second semi-conductor device. each having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in contact with each body, a source of potential, a ilrst pair of impedance elements, each being connected between one terminal of said source and one of vsaid collector electrodes, a second pair of impedance elements, each being connected between the other terminal of said source and one of said base electrodes, said source being so poled as to apply a reverse bias potential between each collector electrode and its associated base electrode, means for applving a forward bias potential between each emitter electrode and its associated base electrode, a ilrst pair of resistors, each being connected between the base electrode of one of said devices and the collector electrode of the other device to provide regeneration, and a Acoupling capacitor connected between said aseguro 13 emitter electrodes, means for applying trigger pulses to said iirst` device, and means for deriving output pulses from said second device in response to said trigger pulses.

3. A bistable multivibrator circuit comprising a first and a second semi-conductor device, each having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in contact with each body, a source of potential, a mst pair of resistors, each being connected between onev terminal of said source and one of said collector electrodes, a second pair of resistors,

each being connected between the other terminal of said source and one of said base electrodes, said source being so poled as to apply a reverse bias potential between each collector electrode and its associated base electrode, means for applying a forward bias potential between each emitter electrode and its associated base electrode, a third pair of resistors, each being connected between the base electrode of one of said devices and the collector electrode of the other device to provide regenerative feedback paths, a coupling impedance element connecting said emitter electrodes, means for applying trigger pulses to said first device, and means for deriving output pulses from said second device.

4. A bistable multivibrator circuit comprising a rst and a second semi-conductor device, each having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in contact with each body, a source of potential, a

`rst pair of resistors, each being connected between one terminal of said source and one of said collector electrodes, a second pair of resistors, each being connected between the other terminal of said source and one of said base electrodes, said source being so poled as to apply a reverse bias potential between each lcollector electrode and its associated base electrode, means for applying a forward bias potential between each emitter electrode and its vassociated base electrode, including a third pair of resistors, each being connected in circuit with one of said emitter electrodes, a fourth pair of resistors, each be ing connected between the base electrode of one of said devices and the collector electrode of the other device to provide regeneration, a coupling capacitor connected between said emitter electrodes, means for applying trigger pulses to the base electrode of said first device, said capacitor facilitating the transfer of said trigger pulses from the base electrode of said first device to said second device, and means for deriving output pulses from said second device.

5. A bistable multivibrator circuit comprising a :first and a second semi-conductor device, each having a semi-conducting body. a base electrode, an'emitter electrode and a collector electrode in contact with each body, a source of potential, a

first pair of resistors, each being connected betrodes, a fourth pair of resistors. each being connected between the base electrode of oneof said devices and the collector-electrode of the other device, a coupling capacitor connected between said emitter electrodes, means for applying trigger pulses to the base electrode o f said first 'device, and means for deriving output pulses from the collector electrode of said second device,

Va first and a second semi-conductor device, each having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in contact with each body, a source of potential, a ilrst pair of resistors, each being connected between one terminal of said source and one oi' said collector electrodes. a second pair of resistors, each being connected between the other terminal of said source and one of said base electrodes, said source being so poled as to apply a reverse bias potential between each collector electrode and its associated base electrode, means for applying a forward bias potential between each emitter electrode and its associated base electrode including a third pair of resistors, each being connected in circuit with one of said emitter electrodes, a fourth pair of resistors, each being connected between the base electrode of one of said devices and the collector electrode of the other device, a coupling capacitor connected between said emitter electrodes, means for applying trigger pulses to the base electrode of said first device, and means for deriving output pulses from the collector electrode of said second device, the resistance of the resistor connected to the base electrode of said first device being larger than the resistance of the resistor connected to the base electrode of said second device, and the resistance of the resistor connected between' the base electrode of said first device and the collector electrode of said second device being smaller than the resistance of the resistor connected between the base electrode of said second device and the collector electrode of said rst device, thereby to facilitate the transfer of said trigger pulses from the base electrode of said rst device to the collector electrode of said second device.

7. In an electronic impulse counter, a counter stage including a bistable multivibrator circuit comprising a first and a second semi-conductor device, each having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in contact with each body, a. source of potential, a rst pair of resistors, each being connected between one terminal of said source 4and one of said collector electrodes, a second pair of resistors, each being connected between the other terminal of said source and one of said base electrodes, said source being so poled as to apply a reverse bias potential between each collector electrode and its associated base electrode, a third pair of resistors, each having one terminal connected to one of said emitter electrodes, a further resistor con-I nected between the other terminals of said third pair of resistors and sad other terminal of said source, a first capacitor connected in shunt with i said further resistor, a. fourth pair of resistors, each being connected between the base electrode of one of said devices and the collector electrode of the other device, a second coupling capacitor connected between said emitter electrodes, means fOr applying trigger pulses to the buse electrode of said i'lrst device, and means including a, ffg

ferentiating network and a clipper for deriving output pulses from the collector electrode of said second device and for impressing said output pulses on a. succeeding counter stage. 

